Cassidy has revved up a social media campaign in an effort to win the homecoming crown at Marina High School in Huntington Beach, joining a growing but still-thin group of transgender teens across the country who see an opportunity to shake up gender norms by competing in what's long been a tradition-bound, sex-segregated American staple.

"If I win it would mean that the school recognizes me as the gender I always felt I was," Cassidy said.

Assigned male at birth but knowing she wasn't a boy, the teen walked through the glass entrance of Marina High in August for the first time as Cassidy Lynn Campbell.

As far back as Cassidy can remember she was drawn to dolls and pink dresses.

"I felt like I was already a girl, so I was confused as to why my mom would cut my hair," Cassidy said. "I didn't understand why she would make me wear shorts and shirts when I wanted to wear dresses and skirts."

She briefly identified as transgender in middle school, but the term seemed to confuse her peers and succeeded in turning her into an outcast. So she just told classmates she was gay.

During her freshman year she started watching YouTube videos made by transgender women.

"They were so unique, so different and beautiful," the 16-year-old said. "That's when I started thinking this could be an option for me."

On Halloween of her sophomore year Cassidy dressed up as a girl, figuring it would be the easiest time to express herself. On a few occasions that year and the next, she went to school in a dress or skirt.

But it still felt less than honest.

"I decided I wasn't happy being a drag queen and being a boy," Cassidy said. "I would dread taking off my wig."

Without telling her mother or consulting a doctor, she began taking hormone blockers that she ordered online.

One night, about three months ago, she came clean to her mom.

"I was crying. That's when I told her, 'I'm taking testosterone blockers and I'm going to start estrogen soon with or without your consent,'" she recalled.

Her mom, Christine Campbell, told her she'd support her. Her father, slower to warm to the change, has not discouraged her. The teen's now on hormone blockers and taking estrogen injections prescribed by an endocrinologist.

She's watched her body change, but the most drastic change has been psychological, she said.

"I didn't just change physically; everything changed," she said.

On Friday, at Marina High's homecoming pep rally, the field of 10 homecoming queen candidates will be thinned to five. Hours later, the queen will be crowned at the school's football game. Her mother will accompany her onto the field if Cassidy is a finalist.

On her bed lies a black leather and chiffon dress, which she plans to wear to the game. Next to it is a bohemian patterned dress, with three-quarter-length sleeves. That, she'll wear to Saturday's homecoming dance.

Standing in front of a mirror that's almost as tall as the ceiling and talking about Britney Spears, Cassidy is just like most high school girls, but these moments of liberation are broken by worries over health complications or even being attacked because of her transition.

"It's worth it because I lived a full life," Cassidy said, "I would die as the person I wanted to be, rather than die in vain as a boy."

The risks of taking estrogen are low, but adolescents and their parents are repeatedly counseled about the possibility of blood clots and liver damage, said Johanna Olson, medical director at the Center for Transyouth Health and Development at Children's Hospital Los Angeles.

"It's a medical necessity," Olson said. "It can't be framed as a choice." she said.

Cassidy's transition has forced her to grow up faster than other kids, her mother said while dicing tomatoes in the family kitchen.

"I don't want her to be who she is, and my religion says it's wrong," said her mother, a self-described born-again Christian. "But I think in the end, love is letting her be who she wants to be."

School officials have not stood in Cassidy's way.

"If Marina High School is to make high-profile news during its homecoming week this year," Principal Paul Morrow said in a statement, "then we are proud that the message is one of equity and individual respect."

Cassidy believes she has a good shot at being crowned.

"But with all the attention, I realized it's bigger than me," she said. "I'm doing this for the kids who can't be themselves."